ios - NSInputStream 缓冲区的大小

Question

我正在尝试使用 NSInputStream 通过 TCP 套接字连接接收数据。在服务器端，我先发送数据大小，然后再发送数据本身。在 iOS 客户端，我需要从 NSInputStream 中提取前 4 个字节，因为我需要检查数据大小是否已完全接收，但我遇到了问题:

...
case NSStreamEvent.HasBytesAvailable:
 if ( aStream == inputstream){    
   while (inputstream.hasBytesAvailable){                    
      var readBufferRef         = UnsafeMutablePointer<UnsafeMutablePointer<UInt8>>()
      var readBufferLengthRef   = 0
      let readBufferIsAvailable = inputstream.getBuffer(readBufferRef, length: &readBufferLengthRef)
...
    }
}
break

收到数据后readBufferLengthRef总是等于0。

怎么可能？

如何获取 NSInputStream 缓冲区的大小？

更新:

代码:

case NSStreamEvent.HasBytesAvailable:
            NSLog("HasBytesAvaible")
            var buffer = [UInt8](count: 1024, repeatedValue: 0)
            if ( aStream == inputstream){

                while (inputstream.hasBytesAvailable){

                    var readBufferRef: UnsafeMutablePointer<UInt8> = nil
                    var readBufferLengthRef = 0
                    let readBufferIsAvailable = inputstream.getBuffer(&readBufferRef, length: &readBufferLengthRef)
                   //debugger: readBufferLengthRef = (int)0
                }
            }
break

Answer 1

在您的代码中，readBufferRef被定义为“指向指针的指针”但从未分配过，因此它是 NULL 指针。

你应该做的是传递一个地址 UnsafeMutablePointer<UInt8>作为函数的 inout 参数(假设 Swift 2):

var readBufferRef: UnsafeMutablePointer<UInt8> = nil
var readBufferLengthRef = 0
let readBufferIsAvailable = inputStream.getBuffer(&readBufferRef, length: &readBufferLengthRef)

返回时，readBufferRef设置为流的读取缓冲区(直到下一次读取操作有效)，并且 readBufferLengthRef包含可用字节数。